Nearly a third of world's cacti face extinction, says IUCN

Nearly a third of the world’s cacti are facing the threat of extinction, according to a shocking global assessment of the effects that illegal trade and other human activities are having on the species.

 Cacti are a critical provider of food and water to desert wildlife ranging from coyotes and deer to lizards, tortoises, bats and hummingbirds, and these fauna spread the plants’ seeds in return.

But the International Union for the Conservation of Nature (IUCN)‘s first worldwide health check of the plants, published today in the journal Nature Plants, says that they are coming under unprecedented pressure from human activities such as land use conversions, commercial and residential developments and shrimp farming.

But the paper said the main driver of cacti species extinction was the: “unscrupulous collection of live plants and seeds for horticultural trade and private ornamental collections, smallholder livestock ranching and smallholder annual agriculture.”

The findings were described as “disturbing” by Inger Andersen, the IUCN’s director-general. “They confirm that the scale of the illegal wildlife trade – including the trade in plants – is much greater than we had previously thought, and that wildlife trafficking concerns many more species than the charismatic rhinos and elephants which tend to receive global attention.”

The conservation group now judges cacti the fifth most threatened species on its red list of endangered flora and fauna, and is calling for an urgent ramping up of international efforts to tackle the illegal wildlife trade. Three of the IUCN’s five most threatened species to date are plants.

Cacti are almost always succulents but unlike most others, they store water in their stems alone, enabling them to survive extreme droughts. The plants can be as small as one centimetre in diameter and grow above 19 metres in height. Well over half of the species are used by humans for display ornamentation, food or medicine.

Almost 1,500 types of cactus were surveyed by the IUCN specialists over a five-year period, mostly in the Americas, where the plant is endemic.

Some, like the once-ubiquitous Echinopsis pampana, have seen population drops of at least 50% in Peru, due to plunder for the ornamental plant trade. The species is now listed as endangered.

“The results of this assessment came as a shock to us,” said Barbara Goettsch, the study’s lead author. “We did not expect cacti to be so highly threatened and for illegal trade to be such an important driver of their decline.”

Cacti are often dug up and exported off the books to Europe and Asia where rare species such as Ariocarpus can sell at prices of up to $1,000 (£660) a plant, Goettsch said.

Tackling the smugglers is a daunting task as the prickly cargo can be smuggled in suitcases or even socks. While countries such as Peru have made progress in blocking the illicit trade, the IUCN is calling for stricter implementation of the Convention on International Trade in Endangered Species (Cites) in the ‘hotspots’ of Uruguay, Brazil and Chile. Mexico has made advances but still has work to do, according to Goettsch.

Despite their charismatic flowers, and iconic status in popular culture, cacti are often overlooked in conservation planning. The report calls for a broadening of arid land protection to deal with human activities such as construction, quarrying and aquaculture.

Exeter University’s Professor Kevin Gaston, who co-led the assessment, said that the results showed how important funding for further scientific assessments is. “Only by so doing will we gain the overall picture of what is happening to them at a time when, as evidenced by the cacti, they may be under immense human pressures.”

Osmanthus

Osmanthus is a genus of about 30 species of flowering plants in the family Oleaceae. Most of the species are native to eastern Asia (China, Japan, Indochina, the Himalayas, etc.) with a few species from the Caucasus, New Caledonia, Sumatra, and North America (Mexico, Central America, southeastern United States)

Osmanthus range in size from shrubs to small trees, 2–12 m (7–39 ft) tall. The leaves are opposite, evergreen, and simple, with an entire, serrated or coarsely toothed margin. The flowers are produced in spring, summer or autumn, each flower being about 1 cm long, white, with a four-lobed tubular-based corolla ('petals'). The flowers grow in small panicles, and in several species have a strong fragrance. The fruit is a small (10–15 mm), hard-skinned dark blue to purple drupe containing a single seed.

Osmanthus are popular shrubs in parks and gardens throughout the warm temperate zone. Several hybrids and cultivars have been developed. Osmanthus flower on old wood and produce more flowers if unpruned. A pruned shrub often produces few or no flowers for one to five or more years, before the new growth matures sufficiently to start flowering.

In Japan, sweet osmanthus (gin-mokusei) is a favorite garden shrub. Its small white flowers appear in short-stalked clusters in late autumn. It has an intense sweet fragrance. A variant with deep golden flowers (kin-mokusei) is also popular.

The flowers of O. fragrans are used throughout East Asia for their scent and flavour, which is likened to apricot and peach.

In China, osmanthus tea (guìhuāchá) combines sweet osmanthus flowers with black or green tea leaves. Traditional Chinese medicine claims that osmanthus tea improves complexion and helps rid the body of excess nitric oxide, a compound linked to the formation of cancer, diabetes, and renal disease.

Osmanthus wine flavours huangjiu or other rice wines with full osmanthus blossoms and is traditionally consumed during the Mid-Autumn Festival.

Alys Fowler: the best way to beat weeds

Dandelions are beastly weeds. Photograph: Alamy

Weeds are often thought of as being unpredictable, with an ability to turn up anywhere and take over. In fact, they are quite the opposite: entirely predictable and wholly reliable. Give them bare ground and they will appear; thus, the first rule of weeding is cover your work. If you are not going to be back at that spot for a couple of weeks, cover the soil with cardboard, black plastic, mulch, or sow green manure. Don’t give the weeds a new playground.

All weeds exploit two strategies to reproduce: by spreading stems or roots, or scattering seed. If you can’t get round to weeding out the roots, pull off the flower heads. But be nice; pollinators love weeds that are rich in nectar and pollen. If possible, let them flower, then pull off the flower heads before they set seed. Rot the seed heads down in a bucket before adding to the compost, as immature weed seeds will happily mature on top of the compost heap if they are left with enough flower stalk.

Seeds can travel long distances. They hitch a ride on the wind or a visitor, and arrive unannounced in your garden. Annual weeds rely on this strategy to get anywhere, while perennials can fall back underground to keep marching on. We fear this lot.

The beastly types are brambles (rooting stems), buttercups (runners or stolons – stems that creep along the ground), ground elder and bindweed (rhizomes – subterranean stems), dock and dandelion (tap roots), mare’s tail or Japanese knotweed (both rhizomes) and creeping thistles (spreading roots and seed). If you leave bits of root behind as you dig, they will resprout.

The biggest weeds probably will have to be dug out nonetheless. “Lasagne gardening” – where you layer sheets of cardboard and rough organic matter on top of the soil – can defeat them, or at least loosen the soil, so it makes digging them out a more joyous task. The bigger the weeds, the more layers of cardboard you will need.

Lasagne gardening works better than weed-suppressing membrane because it enriches the soil and doesn’t leach petrochemicals into the ground. Worms love lasagne gardening because it provides them with new food; they don’t feel the same about plastic. Both systems work by weakening plants through lack of light. Some plants with very deep roots keep going for longer than you’d expect, so if in doubt, add another layer. This way you will also bury weed seeds, which tend to need light to germinate.
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If that doesn’t appeal, get a goat, rabbits, chickens, or a strimmer. My mother’s battle cry used to be “off with their heads”: eventually, you exhaust the roots.

If your weeds are running through the roots of shrubs or herbaceous perennials, the task is more difficult. Picking at new growth will slow them down, but you must be vigilant to win. Digging up shrubs and perennials in autumn, washing the roots and picking out the offending types is laborious but effective. Glyphosate and the like isn’t nearly as effective as it would like you to think it is.

You should come to your garden in the spirit of generosity to all that grows there.

• Listen to Alys on our gardening podcast at theguardian.com/sowgrowrepeat.

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Gardens: what to do this week

Clematis 'Big Brother': 'Its blooms are mammoth.'

Visit this

Whether you’re mad for mahonia or crazy about chrysanthemums, the national collection of your favourite plants is somewhere in the UK. Conservation charity Plant Heritage supports more than 600 national collections, helping to keep threatened plants in cultivation and promote biodiversity in our gardens.

Revive this

You planted a hydrangea, it flourished all spring, but now on hot days its leaves are wilting. Hydrangeas are the first plants in the garden to suffer when the soil dries out. Give them a long drink, then mulch heavily; if they still sulk once established, move to a moister spot come winter.

Plant this

Breeders just can’t leave clematis alone, resulting in ever-bigger blooms that won’t collapse at the first drop of rain. Join the clematis revolution by investing in new variety ‘Big Brother’. At 25cm across, its blooms are mammoth; even better, it flowers twice, in late spring and late summer. Height and spread 1.5m x 90cm. To order one jumbo plug for £14.99, or two jumbo plugs for £19.99, call 0330 333 6856 quoting ref GU359. Or shop online at theguardian.com/offers/plants. All orders include free p&p. Dispatched August to September.

Gardens: seasons in the sun

Drying game: evening primrose. Photograph: Alamy

I am blessed with our soil here – two generations ago the land was market gardens that provided fruit and veg for Bath. When there’s enough rain to keep the hearty south-facing slopes moist, my plants grow athletically, and I have to keep them in check.

In a dry summer such as this, however, our sunny slopes provide challenges. My American swamp lilies are half the height they should be and even though the hellebores are snuggled in the shade of the willows, their rosettes are splayed with thirst.

When building the new vegetable garden, I included a water-harvesting tank to save rainwater from the barn’s roof. Harvesting water is a discipline I encourage my clients to build into their gardens, to raise awareness that it is a finite resource, and also because rainwater is better for your plants.

Bronze fennel. Photograph: Alamy

I made the new vegetable garden by cutting into the land and creating a terraced bank. The steep rubbly slopes that fall away are made with the subsoil from the excavations and sown with a wild-flower mix, which as I write is in its first summer and filled with bees. The wild flowers prefer the poor soil to our rich ground and the grasses are lovely when they dry to tawniness.

Beyond the garden, between two outbuildings, is an area that was backfilled with brash to provide dry access to the compost heaps beyond. The pockets of soil up close to the buildings were given to plants that would do better in good ground.

‘Miss Willmott’s Ghost’. Photograph: Alamy

Being hungry for as many different habitats on the land here, I didn’t add any topsoil to the areas either side of the path. I wanted a contrast to the heartiness elsewhere, and selected a range of plants that would thrive in the free-draining ground. Sea kale, with its young foliage the colour of red cabbage and later sprawl of honey-scented flowers, Baptisia ‘Chocolate Chip’, in dusky tones that suit the rusted tin, and a good hybrid Phlomis called ‘Edward Bowles’. This is creamy yellow like its parent P russelliana, but takes on a semi shrubby form from P fruticosa. Euphorbia ‘Copton Ash’ is new to me with low, glaucous foliage and lime-green flowers. Drifting, as if self-sown, crimson Dianthus cruentus, lilac Centranthus locoqi and Beupleurum perfoliatum mingle throughout.

I planted openly to broadcast a seed mix I’d made up of plants that I knew would take to the dry, loose shingle. Evening primrose, bronze fennel, sweetly scented Matthiola incana ‘Alba’ and ‘Miss Willmott’s Ghost’, Eryngium giganteum. Beth’s poppy, a gift from Fergus Garret at Dixter, passed in turn to him from Beth Chatto from her dry garden was already up and rejoicing in the stony ground this April. It is a nice reminder of Beth’s mantra: the right plant in the right place, and you can enjoy a dry summer.

Get growing

When planting a dry position do so when there is moisture around, in the spring or autumn. Soak the pots in water until the bubbles stop rising to the surface, and try to have courage to let the plants find their way thereafter.